Electric initiator

Abstract

An electric initiator, such as a detonator, primer or squib, has a plastic case, a metallic inner cup, an explosive charge and a coaxial plug assembly which includes a conductive pin, a conductive sleeve surrounding the pin and spaced therefrom, an insulator which is bonded to both the pin and the sleeve, and a bridge wire connecting the two electrodes. The initiator also includes two lead wires, one welded or soldered to each electrode. This initiator is easy to assemble automatically and is highly resistant to accidental firing by static electricity.

What is claimed is: 
     
       1. An electric initiator comprising: a. a cup-shaped nonconductive cylindrical outer case open at one end and closed at the other end;   b. a cylindrical metallic inner cup open at one end and closed at the other end, said cup being of one piece construction comprising a cylindrical wall and an end wall at one end, the thickness of the end wall being at least as great as the thickness of the cylindrical wall, the open ends of said nonconductive case and said inner cup being oriented in the same direction, said outer case completely surrounding the side and closed end of said inner cup so as to prevent accidental grounding of said inner cup;   c. an explosive charge within said inner cup;   d. a coaxial plug assembly within said inner cup adjacent to said explosive charge, said assembly comprising 1. an elongated, longitudinally extending conductive center pin;   2.     
     
     
       2. a conductive sleeve surrounding said pin and coaxial therewith but spaced therefrom, said conductive sleeve being in engagement with said inner cup, 3. a refractory insulator separating said pin from said sleeve, said insulator forming refractory-to-metal seals with said pin and said conductive sleeve, and   4. a bridge element connecting said pin with said sleeve, said bridge element being in proximity with said explosive charge;   e. means forming a moisture proof seal between said inner cup and said sleeve;   f. a pair of lead wires extending through the open end of said case;   g. means connecting one of said lead wires to said pin;   h. means connecting the other of said lead wires to said sleeve; and   
     
     
       i. potting material sealing the open end of said case. 2. An initiator according to claim 1 in which said sleeve has two cylindrical portions of different diameters and a shoulder therebetween, the portion of larger diameter being nearer the closed end of said case. 
     
     
       3. An initiator according to claim 1 in which the ends of the center pin and the conductive sleeve nearest the closed ends of said outer case and said inner cup are essentially coplanar and in which said bridge element is connected to said ends of said center pin and said sleeve. 
     
     
       4. An initiator according to claim 1 in which said insulator is glass. 
     
     
       5. An initiator according to claim 1 in which said moisture proof seal is a fusion seal.